The present invention relates to a novel wear resistant resin composition. More specifically, it relates to a wear resistant resin composition which is excellent in wear resistance and heat resistance, has rubber-like physical properties with good balance between compressive stress and compressive stress relaxation, and can be re-molded.
Out of thermoplastic resins, polyolefin resins are excellent particularly in chemical resistance, insulating properties, heat stability and the like and therefore widely used as raw materials for molding various products.
Out of such polyolefin resins, thermoplastic polyolefin resins having rubber-like properties are used for various purposes that require flexibility, such as interior and exterior parts for an auto-movil, materials for covering rod-like and linear products which are extrusion molded at a high speed, and further mud guards and desk mats.
For the above applications, an inorganic filler is blended into a polyolefin to improve the mechanical strength of the obtained molded product or provide flame retardancy to the molded product.
However, the above polyolefin has such a problem that its wear resistance is lowered by blending the inorganic filler. Particularly when the flexural modulus of the obtained molded product is 2,000 MPa or less, there is seen a strong tendency that a contact portion of the molded product wears away through repetitions of its sliding contact with the same molded product or another member.
To improve the wear resistance of a molded product of a polyolefin containing an inorganic filler, JP-A 2-53846 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and U.S. Pat. No. 5,418,272 have proposed a resin composition which comprises a polyolefin-based resin, a thermoplastic elastomer having an organic acid group bonded by acid modification and an inorganic filler (inorganic flame retardant).
The above polyolefin-based resin is a copolymer or rubber essentially composed of ethylene.
The above acid modification technology is aimed to improve the adhesion of the composition to the inorganic filler by bonding the organic acid group to the polyolefin or to improve wear resistance by partly crosslinking the inorganic filler with a metal.
However, a composition obtained by adding an ethylene-based resin to the above polyolefin to achieve flexibility is still unsatisfactory in terms of heat resistance.
When a resin having a high melting point such as polypropylene is used as a matrix resin, a large amount of a soft resin such as the above ethylene-based resin or rubber material must be added to achieve flexibility. The obtained composition has low heat resistance and further low mechanical properties such as tensile strength like the above composition.
It is an object of the present invention to provide a wear resistant resin composition which is a polyolefin composition containing an inorganic filler and excellent in wear resistance, rubber-like physical properties and heat resistance, and can be re-molded.
Other objects and advantages of the present invention will be apparent from the following description.
According to the present invention, the above objects and advantages of the present invention are attained by a wear resistant resin composition comprising: (A) 100 parts by weight of a modified microblend obtained by bonding an organic acid group to a microblend (may be referred to as xe2x80x9cspecific microblendxe2x80x9d hereinafter) consisting of 1 to 70 wt % of polypropylene and 99 to 30 wt % of a propylene-ethylene random copolymer (may be referred to as xe2x80x9cP-E random copolymerxe2x80x9d hereinafter) consisting of 15 to 50 mol % of an ethylene polymer unit and 85 to 50 mol % of a propylene polymer unit, or a mixture of the microblend and the modified microblend, the concentration of the organic acid group in the modified microblend or the mixture being 0.01 to 1 mmol based on 1 g of the microblend, and the microblend containing 10 to 90 wt % of a component eluting at a temperature of xe2x88x9240 to +30xc2x0 C. (may be referred to as xe2x80x9clow-temperature eluting componentxe2x80x9d hereinafter) based on the total of all the eluting components fractionated by temperature rise elution fractionation using o-dibromobenzene as a solvent; and
(B) 1 to 1,000 parts by weight of at least one filler selected from the group consisting of a fibrous filler and a lamellar filler,
and having a flexural modulus of 2,000 MPa or less.
According to the present invention, there is also provided a wear resistant resin composition having more improved heat resistance by further blending polypropylene as a resin composition.
In the present invention, the flexural modulus is a value measured in accordance with JIS K7203.
The temperature rising elution fractionation used in the present invention is a means of analyzing the composition or the distribution of stereoregularity or non-crystallinity of a crystalline polymer such as a polyolefin and carried out by the following operation. A high-temperature solution of the specific microblend is first introduced into a column filled with a filler such as diatomaceous earth or glass beads, and components having higher melting points are crystallized one after another on the surface of the filler by gradually reducing the temperature of the column. Thereafter, components having lower melting points are eluted and dispensed one after another by gradually increasing the temperature of the column. In the present invention, the rate of reducing the temperature of the column in the above measurement is 2xc2x0 C./hr. The rate of increasing the temperature of the column is 4xc2x0 C./hr.
As for the concrete operation, please refer to the Journal of Applied Polymer Science; Applied Polymer Symposium, 45, 1-24 (1990). In the fractionation of a copolymer composition by the above method, a resin composition having no crystallinity or extremely low crystallinity is fractionated at a relatively low temperature lower than normal temperature and components having higher crystallinity are fractionated along with a rise in elution temperature. The amount of each fractionated component can be calculated from an elution curve drawn by plotting elution temperature as the axis of abscissa and integrated weight percentage as the axis of ordinate.
In the present invention, it is important that the specific microblend should satisfy the following conditions at the same time.
(1) The amount of a component eluting at a temperature of xe2x88x9240 to +30xc2x0 C. is 10 to 90 wt %, preferably 30 to 80 wt % based on the total of all the eluting components fractionated by temperature rising elution fractionation using an o-dibromobenzene solvent.
(2) The specific microblend consists of 1 to 70 wt %, preferably 1 to 40 wt % of polypropylene and 99 to 30 wt %, preferably 99 to 60 wt % of a propylene-ethylene random copolymer which consists of 15 to 50 mol %, preferably 15 to 40 mol % of an ethylene polymer unit and 85 to 50 mol %, preferably 85 to 60 mol % of a propylene polymer unit.
That is, the above specific microblend is characterized in that a sufficiently large amount of a low-temperature eluting component is contained although the content of the propylene polymer unit in the P-E random copolymer is large. Due to this feature, the obtained wear resistant resin composition exhibits excellent wear resistance and rubber-like physical properties and exhibits superior in heat resistance to a conventional wear resistant resin composition comprising a polyolefin essentially composed of an ethylene polymer unit. Due to use of the above specific microblend, the wear resistant resin composition of the present invention is also excellent in physical properties such as tensile strength.
When the low-temperature eluting component of the above specific microblend is contained in an amount of less than 10 wt %, flexibility lowers as a large amount of a crystal component is contained in the resin, thereby making it difficult to obtain a resin composition having a flexural modulus of 2,000 MPa or less which the present invention is directed to.
When the low-temperature eluting component of the above specific microblend is contained in an amount of more than 90 wt %, heat resistance lowers, the stickiness of the resin becomes high, and blocking tends to occur.
When the specific microblend has the following stepwise distribution of eluting components fractionated by temperature rising elution fractionation in the present invention, it further improves wear resistance and rubber-like physical properties advantageously.
That is, the specific microblend is particularly preferably a microblend which consists of a component eluting at a temperature of xe2x88x9240xc2x0 C. or more and less than 20xc2x0 C. (component xe2x80x9caxe2x80x9d) in an amount of 20 to 80 wt %, a component eluting at a temperature of 20xc2x0 C. or more and less than 100xc2x0 C. (component xe2x80x9cbxe2x80x9d) in an amount of 10 to 70 wt % and a component eluting at a temperature higher than 100xc2x0 C. (component xe2x80x9ccxe2x80x9d) in an amount of 1 to 40 wt %, all of which are fractionated by temperature rise elution fractionation using an o-dichlorobenzene solvent (the total of the components xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d is 100 wt %).
That is, the component xe2x80x9caxe2x80x9d contributes to the development of the flexibility of the obtained wear resistant resin composition. When the amount of the component xe2x80x9caxe2x80x9d is smaller than 20 wt %, the flexibility of the obtained wear resistant resin composition is easily impaired and when the amount is larger than 80 wt %, sufficient heat resistance is hardly obtained. To obtain higher flexibility, the amount of the component xe2x80x9caxe2x80x9d is preferably 30 to 70 wt %.
The component xe2x80x9cbxe2x80x9d develops compatibility between the components xe2x80x9caxe2x80x9d and xe2x80x9ccxe2x80x9d. As a result, it is effective in maintaining good balance between the flexibility and heat resistance of the obtained wear resistant resin composition. When the amount of the component xe2x80x9cbxe2x80x9d is smaller than 10 wt %, the flexibility of the obtained wear resistant resin composition tends to lower and when the amount is larger than 70 wt %, the heat resistance of the composition is apt to be unsatisfactory. To maintain good balance between the flexibility and heat resistance of the obtained wear resistant resin composition, the amount of the component xe2x80x9cbxe2x80x9d is preferably 15 to 50 wt %.
The component xe2x80x9ccxe2x80x9d is effective in providing excellent heat resistance which is the feature of polypropylene to the obtained wear resistant resin composition. When the amount of the component xe2x80x9ccxe2x80x9d is smaller than 1 wt %, the heat resistance of the obtained wear resistant resin composition tends to lower, thereby making it difficult to attain the object of the present invention. When the amount of the component xe2x80x9ccxe2x80x9d is larger than 40 wt %, the flexibility of the obtained wear resistant resin composition is easily impaired. To obtain higher heat resistance, the amount of the component xe2x80x9ccxe2x80x9d is preferably 5 to 30 wt %.
In the specific microblend of the present invention, the polypropylene corresponds to the component xe2x80x9ccxe2x80x9d eluting by the above temperature rising elution fractionation (may be abbreviated as TREF hereinafter). The polypropylene may be a homopolymer of propylene, a propylene-xcex1-olefin random copolymer and propylene-xcex1-olefin block copolymer comprising an xcex1-olefin polymer unit other than propylene in an amount of 10 mol % or less.
They may be used alone or in admixture of two or more.
Examples of the xcex1-olefin include ethylene, butene-1,1-pentene, 1-hexene, 1-octene, 3-methyl-1-butene and 4-methyl-1-pentene.
In the specific microblend of the present invention, the P-E random copolymer substantially corresponds to the components xe2x80x9caxe2x80x9d and xe2x80x9cbxe2x80x9d eluting by the above TREF. It is important in attaining the object of the present invention that the amount of the ethylene polymer unit should be 15 to 50 mol % and the amount of the propylene polymer unit should be 85 to 50 mol % based on the P-E random copolymer. More preferably, the amount of the propylene polymer unit is 85 to 60 mol % and the amount of the ethylene polymer unit is 15 to 40 mol %.
When the amount of the propylene polymer unit is larger than 85 mol % and the amount of the ethylene polymer unit is smaller than 15 mol %, the flexibility of the obtained wear resistant resin composition is impaired and when the amount of the propylene polymer unit is smaller than 50 mol % and the amount of the ethylene polymer unit is larger than 50 mol %, the heat resistance of the obtained wear resistant resin composition is impaired.
In the present invention, the specific microblend may contain an xcex1-olefin polymer unit other than the above propylene polymer unit and ethylene polymer unit in limits that do not change its characteristic properties markedly.
Stated more specifically, it may contain an xcex1-olefin polymer unit such as 1-butene in an amount of 10 mol % or less.
In the present invention, the above specific microblend can be produced by a method described in JP-A 5-320468. JP-A 5-320468 is included in the description of the present invention. The term xe2x80x9cmicroblendxe2x80x9d as used in the present invention can be understood as a mixture of polypropylene and the P-E random copolymer produced by the above method in a molecular order or an order close thereto. The above microblend may also be conventionally called xe2x80x9cpropylene-ethylene block copolymerxe2x80x9d.
In the present invention, the weight average molecular weight of the specific microblend obtained by the above production method is not particularly limited. The weight average molecular weight in terms of polystyrene of the specific microblend is preferably 70,000 to 7,000,000, more preferably 200,000 to 3,000,000, particularly preferably 300,000 to 2,000,000.
The melt flow rate (MFR) of the specific microblend is preferably adjusted to 0.3 to 150 g/10 minutes to be used.
In the present invention, to improve the wear resistance of the soft resin composition which is lowered by the addition of an inorganic filler without preventing an effect obtained by adding the inorganic filler, it is important that a modified microblend should be used by bonding an organic acid group to the specific microblend in a concentration of 0.01 to 1 mmol/g.
That is, when the concentration of the organic acid group bonded to the specific microblend is lower than 0.01 mmol/g, wear resistance lowers disadvantageously. When the concentration of the organic acid group is higher than 1 mmol/g, the effect is not improved, which is not preferred from an economical point of view.
In the above modified microblend, the concentration of the organic acid group bonded to the specific microblend is preferably 0.05 to 0.7 mmol/g, more preferably 0.1 to 0.3 mmol/g.
The type of the above organic acid group is not particularly limited. It is generally an organic acid group provided by an unsaturated organic acid or a derivative such as an acid anhydride thereof.
Examples of the organic acid group include monobasic acids, dibasic acids and acid anhydrides such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, citraconic anhydride and itaconic anhydride. Metal salts, imides, amides and esters of the above unsaturated organic acids may also be used.
To obtain the modified microblend by bonding an organic acid group to the specific microblend, any known method may be used. For example, there are employed a method in which the specific microblend and an unsaturated organic acid or a derivative such as an acid anhydride thereof are contacted to each other in an inactive organic solvent, a method in which a mixture of the specific microblend and an unsaturated organic acid or a derivative such as an acid anhydride thereof is irradiated with radiation such as an electron beam, X-ray, xcex1-ray or xcex3-ray, and a method in which a reaction initiator typified by an organic peroxide is mixed with the specific microblend and an unsaturated organic acid or a derivative such as an acid anhydride thereof and melt mixed. The last method is the most preferred from an industrial point of view.
Examples of the organic peroxide used in the method for obtaining the above modified microblend include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-(t-butylperoxy)hexine-3-di-t-butyl peroxide, cumene hydroperoxide, t-butylhydroperoxide, benzoyl peroxide, lauroyl peroxide, 1,3-bis(t-butylperoxyisobutyl)benzene and xcex1, xcex1-bis(t-butylperoxydiisopropyl)benzene.
To obtain the above modified microblend, a method in which vinyl acetate, acrylic ester, unsaturated carboxylic acid or the like is copolymerized during the polymerization of the above specific microblend may also be employed.
In the present invention, a mixture containing the organic acid group in the above concentration may be prepared by forming a master batch by bonding the organic acid group in an amount larger than 1 mmol based on 1 g of the specific microblend and mixing the master batch with the specific microblend to be used in place of the modified microblend. When this mixture is used, it is to be understood that the amount of the specific microblend which is a standard for the concentration of the organic acid group means the total amount of the specific microblend to be mixed with the modified microblend and the specific microblend before modification.
The mixture of the specific microblend and the modified microblend is preferably a mixture consisting of 10 to 90 wt % of the specific microblend and 90 to 10 wt % of the modified microblend.
In the present invention, polypropylene is preferably added separately in an amount that ensures that the obtained wear resistant resin composition should achieve the above flexural modulus.
Polypropylene is used in an amount of preferably 500 parts or less by weight, more preferably 500 to 33 parts by weight, particularly preferably 330 to 40 parts by weight based on 100 parts by weight of the above modified microblend or the above mixture.
That is, when the amount of polypropylene is larger than 500 parts by weight, the flexibility of the obtained polypropylene-based resin composition is easily impaired and when the amount is smaller than 33 parts by weight, the effect of improving heat resistance tends to lower.
The above polypropylene may be a homopolymer of propylene, a propylene-xcex1-olefin random copolymer or a micloblend consisting of polypropylene and propylene-xcex1-olefin random copolymer comprising an xcex1-olefin polymer unit other than propylene in an amount of 15 mol % or less.
They may be used alone or in admixture of two or more.
Examples of the xcex1-olefin include ethylene, butene-1,1-pentene, 1-hexene, 1-octene, 3-methyl-1-butene and 4-methyl-1-pentene.
The melt flow rate (MFR) of the above polypropylene is preferably 0.3 to 150 g/10 minutes.
In the present invention, a fibrous filler and/or a lamellar filler are/is blended into the above polyolefin resin to develop good balance among compressive stress, compressive stress relaxability and flexural modulus at the time of compression deformation.
Any known fibrous filler may be used in the present invention. The fibrous filler has an average fiber diameter of preferably 0.1 to 2 xcexcm, more preferably 0.5 to 1.0 xcexcm, and an aspect ratio of preferably 3 to 1,000, more preferably 15 to 80.
When the average fiber diameter is smaller than 0.1 xcexcm, dispersibility may become poor, thereby worsening the appearance of the obtained composition. When the average fiber diameter is larger than 2 xcexcm, the diameter becomes too large, thereby worsening the appearance of the obtained molded product.
When the aspect ratio is lower than 3, the effect of improving compressive stress becomes insufficient. When the aspect ratio is higher than 1,000, the appearance of the molded product worsens disadvantageously.
The amount of the above fibrous filler is generally 1 to 1,000 parts by weight, preferably 20 to 600 parts by weight based on 100 parts by weight of the specific microblend or a mixture of the modified microblend and the specific microblend. It is more preferably 1 to 300 parts by weight, particularly preferably 20 to 200 parts by weight based on 100 parts by weight of the total of all the resin components comprising the specific microblend, a mixture of the modified microblend and the specific microblend, or the total of the specific microblend or a mixture of the modified microblend and the specific microblend and polypropylene. When the amount of the fibrous filler is smaller than 1 part by weight based on 100 parts by weight of the specific microblend or a mixture of the modified microblend and the specific microblend, the compressive stress of the molded product hardly improves and when the amount is larger than 1,000 parts by weight, the appearance of the molded product worsens disadvantageously.
Examples of the fibrous filler include fibrous magnesium oxysulfate, potassium titanate fibers, magnesium hydroxide fibers, aluminum borate fibers, calcium silicate fibers, calcium carbonate fibers, glass fibers, carbon fibers, metal fibers, asbestos, wollastonite, gypsum fibers, mineral fibers, and organic fibers (such as polyamide fibers and polyester fibers). Out of these, fibrous magnesium oxysulfate is preferred.
The surface of the fibrous filler may be treated with a known surface treatment agent to improve its dispersibility. Examples of the surface treatment agent include fatty acid metal salts and coupling agents. Out of these, the surface of the fiber is preferably treated with magnesium stearate or sodium stearate to improve its dispersibility. Known adhesive resins may also be used.
Any known lamellar filler may be used in the present invention. The lamellar filler has an average particle diameter obtained by particle size distribution measurement using a laser diffraction scattering method of preferably 0.5 to 10 xcexcm, more preferably 1 to 6 xcexcm, and an aspect ratio of preferably 3 to 200, more preferably 15 to 80.
When the particle diameter is smaller than 0.5 xcexcm, the dispersibility of the lamellar filler may be poor. When the particle diameter is larger than 10 xcexcm, the appearance of the obtained composition may worsen disadvantageously.
When the aspect ratio is smaller than 3, the effect of improving compressive stress may become unsatisfactory. When the aspect ratio is larger than 200, the appearance of the molded product may worsen disadvantageously.
The amount of the lamellar filler is generally 1 to 1,000 parts by weight based on 100 parts by weight of the specific microblend or a mixture of the modified microblend and the specific microblend. It is preferably 1 to 300 parts by weight, more preferably 10 to 250 parts by weight based on 100 parts by weight of the total of all the resin components comprising the specific microblend, a mixture of the modified microblend and the specific microblend, or the total of the specific microblend or a mixture of the modified microblend and the specific microblend and polypropylene.
When the amount of the lamellar filler is smaller than 1 part by weight, the compressive stress of the molded product does not improve and when the amount is larger than 300 parts by weight, the appearance of the molded product worsens disadvantageously.
Any lamellar filler may be used if it satisfies the above conditions. Examples of the lamellar filler include talc, mica, clay, glass flake, graphite, aluminum flake, kaolin clay, iron oxide, sericite, molybdenum disulfide, barium sulfate, vermiculite, magnesium hydroxide, aluminum hydroxide and hydrotalcite.
The surface of the lamellar filler may be treated with a known surface treatment agent to improve its dispersibility. Examples of the surface treatment agent include fatty acid metal salts and coupling agents. Out of these, the surface of the lamellar filler is preferably treated with magnesium stearate or sodium stearate to improve its dispersibility. Known adhesive resins may also be used.
Further, the fibrous filler and the lamellar filler may be used in combination in any ratio.
In the present invention, the above fibrous filler and lamellar filler preferably serve as an ionically crosslinking agent.
The ionically crosslinking agent acts on the organic acid group contained in the above specific microblend by melt mixing to form an ionically crosslinked structure. The ionically crosslinked structure can provide excellent heat resistance and rubber-like properties to the wear resistant resin composition and makes it possible for the composition to exhibit excellent recyclability although it is a crosslinked product.
In the present invention, the material which functions as an ionically crosslinking agent may be suitably selected from the above fillers. For example, hydroxides of polyvalent metals such as magnesium hydroxide and aluminum hydroxide are particularly preferred.
The above hydroxides have functions as a crosslinking agent and also as a flame retardant and acid trapping agent for catching a free acid after crosslinking when they are added in large quantities.
The existence and degree of ion crosslinking formed by the above ionically crosslinking agent can be confirmed by checking the infrared spectrum of a gel portion. That is, an absorption band based on bonding between a carboxyl group or acid anhydride group and a polyvalent metal ion is formed at 1,560 cmxe2x88x921, whereby it can be confirmed that the above crosslinking reaction has been carried out.
In the wear resistant resin composition of the present invention, the proportion of the gel portion showing the proportion of a crosslinked portion is preferably 10 to 80 wt %, more preferably 20 to 60 wt %.
The proportion of the gel portion in the above wear resistant resin composition can be adjusted by controlling the concentration of an organic acid group in the above modified microblend, the amount thereof, and the amount of the ionically crosslinking agent.
As described above, the wear resistant resin composition of the present invention exerts an extremely marked effect on heat resistance compared with a conventional polyolefin-based elastomer due to the existence of a special gel portion derived from the specific microblend.
Although the function and mechanism that the above effect can be developed by the above gel portion are not made clear in the present invention, it is assumed that they are due to the following fact. The above gel portion contains an ionically crosslinked product of the specific microblend having a special crystallinity distribution and shows an appropriate swelling tendency for a solvent even when its average crosslinking density is made relatively high. Thereby, it shows excellent dispersibility in a matrix resin, excellent heat resistance for conventional TPO as described above and unique rubber-like properties which cannot be achieved with conventional TPO.
A slight amount of a crosslinked product is formed in the gel contained in the wear resistant resin composition of the present invention by a reaction for bonding the organic acid group. The gel in the present invention may contain part of the crosslinked product together with the ionically crosslinked product.
In the present invention, the expression xe2x80x9cgel portion in the wear resistant resin compositionxe2x80x9d means the proportion of an insoluble material obtained after 6 hours of Soxhlet extraction of a sample resin composition cut into strands having a diameter of 2.5 to 3.5 mm with p-xylene.
The gel portion is for a polymer composition and the proportion thereof is calculated by excluding an insoluble component when the polymer composition contains the insoluble component other than a crosslinked polymer, for example, an inorganic material.
In the present invention, the flowability of the wear resistant resin composition at the time of melting is not particularly limited. However, the melt flow rate (may be abbreviated as MFR hereinafter) is preferably 100 g/10 min or less, generally 20 g/10 min or less.
The melt flow rate is a value measured in accordance with JIS K7210.
The wear resistant resin composition of the present invention may contain various additives in limits that satisfy the requirements of the present invention.
For example, a polyolefin resin other than the above specific microblend and polypropylene may be blended. Examples of the polyolefin resin include propylene-ethylene random copolymer, propylene-ethylene block copolymer, high-density polyethylene, intermediate-density polyethylene, low-density polyethylene, linear polyethylene composed of a copolymer of ethylene and an xcex1-olefin having 4 to 10 carbon atoms, ethylene-propylene copolymer (EPDM), ethylene-butene-1 copolymer, propylene-butene-1 copolymer, poly1-butene, poly1-pentene, poly4-methylpentene-1, polybutadiene and polyisoprene.
A resin other than the above polyolefin resins, such as ethylene-vinyl acetate copolymer, ethylene methacrylate, polychloroprene, polyethylenehalide, polypropylenehalide, fluororesin, acrylonitrile-butadiene rubber, polystyrene, polybutadiene terephthalate, polycarbonate, polyvinyl chloride, fluorine rubber, polyethylene terephthalate, polyamide, acrylonitrile-butadiene-styrene copolymer, petroleum resin, petroleum resin-based hydrocarbon such as hydrogenated petroleum resin, terpene resin or hydrogenated terpene resin, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-propylene-butylene-styrene block copolymer or aromatic vinyl-based rubber such as a hydride of the above copolymer may also be blended. The above resin may have the above organic acid group.
These resins as additives are used in an amount of preferably 40 parts or less by weight, more preferably 20 parts or less by weight, particularly preferably 15 parts or less by weight based on 100 parts by weight of the modified microblend or the above mixture containing the same.
The polyolefin resin composition of the present invention may contain a known spherical filler such as zeolite, diatom, calcium carbonate, silica, silicate or glass bead as required in addition to the above filler components. The above fillers may be used in combination of two or more.
The amount of the above filler is preferably 0.1 to 80 parts by weight based on the 100 parts by weight of the total of all the resin components.
The wear resistant resin composition of the present invention may further contain other additives in limits that do not impair the effect of the present invention. The additives include a hindered amine-based thermal stabilizer; hindered amine-based weathering agent; benzophenone-based, benzotriazole-based or benzoate-based ultraviolet light absorber; nonionic, cationic or anionic antistatic agent; bisamide-based or wax-based dispersant; amide-based, wax-based, organic metal salt-based or ester-based lubricant; oxide-based decomposer; melamine-based, hydrazine-based or amine-based metal inactivating agent; bromine-containing organic, phosphate-based, antimony trioxide, red phosphorus-based, silicon-based, silica-based, melamine-based, glass-based or hydrous inorganic flame retardant; organic pigment; inorganic pigment; sorbitol-based, aromatic phosphoric acid metal salt-based or organic acid metal-based transparentizing or nucleating agent; antifogging agent; antiblocking agent; foaming agent; organic filler; and metal ion-based inorganic anti-fungus agent and organic anti-fungus agent. The present invention is not limited by these.
Further, any known phenolic antioxidant may be used in the wear resistant resin composition of the present invention as required with no limitation. Examples of the antioxidant include 2,6-di-t-butyl-4-hydroxyphenol, 2,6-di-t-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol, stearyl(3,5-di-t-butyl-4-hydroxyphenyl)propionate, distearyl(3,5-di-t-butyl-4-hydroxybenzyl)phosphonate, thiodiethylene glycol bis[(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 4,4xe2x80x2-thiobis(6-t-butyl-m-cresol), 2-octylthio-4,6-di(3,5-di-t-butyl-4-hydroxyphenoxy)-s-triazine, 2,2xe2x80x2-methylenebis(4-methyl-6-t-butylphenol), 2,2xe2x80x2-methylenebis(4-ethyl-6-t-butylphenol), bis[3,3xe2x80x2-bis(4-hydroxy-3-t-butylphenyl)butyric acid]glycol ester, 4,4xe2x80x2-butylidenebis(6-t-butyl-m-cresol), 2,2xe2x80x2-ethylidenebis(4,6-di-t-butylphenol), 2,2xe2x80x2-ethylidenebis(4-t-butyl-6-t-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, bis[2-t-butyl-4-methyl-6-(2-hydroxy-3-t-butyl-5-methylbenzyl)phenyl]terephthalate, 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-t-butylbenzyl)isocyanate, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanate, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, 1,3,5-tris[(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanate, tetrakis[methylene(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 2-t-butyl-4-methyl-6-(2-acryloyloxy-3-t-butyl-5-methylbenzyl)phenol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane-bis[xcex2-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], and triethylene glycol bis[xcex2-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate].
The phenolic antioxidant is used in an amount of 0.001 to 1 part by weight, preferably 0.01 to 0.8 part by weight based on 100 parts by weight of the total of all the resin components.
The above phenolic antioxidants may be used alone or in combination of two or more.
When the amount of the above phenolic antioxidant is smaller than 0.001 part by weight, the deterioration of the obtained resin becomes marked, resulting in the yellowed resin. When the amount of the phenolic antioxidant is larger than 1 part by weight, it is not preferred economically.
Any known organic phosphorus-based antioxidant may be used in the wear resistant resin composition of the present invention as required. Examples of the organic phosphorus-based antioxidant include trisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, di(tridecyl)pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, tetra(tridecyl)isopropylidenediphenol diphosphite, tetra(tridecyl)-4,4-n-butylidenebis(2-t-butyl-5-methylphenol)diphosphite, hexa(tridecyl)-1,1xe2x80x2-3-tris(3-t-butyl-4-hydroxy-5-methylphenyl)butane triphosphite, 2,2xe2x80x2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 2,2xe2x80x2-methylenebis(4,6-di-t-butylphenyl)octadecyl phosphate, 2,2xe2x80x2-methylenebis(4,6-di-t-butylphenyl)fluorophosphite and tetrakis(2,4-di-t-butylphenyl)biphenylene diphosphonite.
The organic phosphorus-based antioxidant is used in an amount of 0.001 to 1 part by weight, preferably 0.01 to 0.8 part by weight based on 100 parts by weight of the total of all the resin components.
The above organic phosphorus-based antioxidants may be used alone or in combination of two or more.
When the amount of the organic phosphorus-based antioxidant is smaller than 0.001 part by weight, the deterioration of the resin becomes marked, resulting in the yellowed resin. When the amount is larger than 1 part by weight, it is not preferred economically.
Any known thioether-based antioxidant may also be used in the wear resistant resin composition of the present invention as required. Examples of the thioether-based antioxidant include dialkyl thiodipropionates such as dilauryl, dimyristyl and distearyl esters of thiodipropionic acid, and xcex2-alkylmercaptopropionic acid esters of a polyol such as pentaerythritol tetra(xcex2-dodecylmercaptopropionate).
The thioether-based antioxidant is used in an amount of 0.001 to 1 part by weight, preferably 0.01 to 0.8 part by weight based on 100 parts by weight of the total of all the resin components.
The above thioether-based antioxidants may be used alone or in combination of two or more.
When the amount of the thioether-based antioxidant is smaller than 0.001 part by weight, the deterioration of the resin becomes marked, resulting in the yellowed resin. When the amount is larger than 1 part by weight, it is not preferred economically.
The above phenolic antioxidants, organic phosphorus-based antioxidants and thioether-based antioxidants may be used alone or in combination of two or more if the total amount of the components is 0.001 to 2 parts by weight, preferably 0.01 to 1 part by weight based on 100 parts by weight of the total of all the resin components.
In the present invention, the above components may be mixed by any method generally used for mixing a resin. For example, other resins, additives and filler are added to the above resin in the form of a powder and/or pellet and mixed together by a tumbler, Henschel mixer, Banbury mixer, ribbon feeder or super mixer, and melt mixed by a single-screw or multi-screw extruder (preferably a melt mixer capable of degassing), roll, kneader or Banbury mixer at a melt mixing temperature of 150 to 350xc2x0 C., preferably 190 to 280xc2x0 C. to prepare a pellet.
The addition order of the above components is not particularly limited and may be different from the order of the above method. A master batch containing other additives and filler components condensed in a high concentration may be prepared and mixed.
A molded product which is satisfactory in terms of rubber-like properties with good balance between compressive stress and the value of compressive stress relaxation, wear resistance and heat resistance can be obtained from the wear resistant resin composition of the present invention.
A compressive stress at a distortion of 5% of 0.4 MPa to 20 MPa and a compressive stress relaxation value of 20 to 80% can be achieved and a molded product having the above physical properties is particularly preferred in the present invention.
The measurement of the above compressive stress can be carried out in accordance with the method specified in JIS K7181. In the present invention, the compressive stress is particularly preferably 2 to 15 MPa at a distortion of 5%. The compressive stress at a distortion of 5% is measured at a compression speed of 200 mm/min. A molded product having the above range of compressive stress can further improve buckling resistance while retaining appropriate flexibility.
The measurement of the above compressive stress relaxation value is carried out in accordance with the compression distortion method specified in JIS K7181. The expression xe2x80x9cstress relaxationxe2x80x9d means the reduction rate of stress with the passage of time. In the present invention, the compressive stress relaxation value is particularly preferably 30 to 70%. The compressive stress is measured at a compression speed of 200 mm/min, the value at a distortion of 5% is maintained for 10 minutes, and the stress after 10 minutes is measured to obtain a compressive stress relaxation value by dividing a reduction in stress for 10 minutes by stress at the start of maintaining a compression of 5%. What has the above range of stress relaxation value can further improve the stress absorption characteristics and buckling resistance of a molded product obtained from the polyolefin resin composition of the present invention.
The wear resistant resin composition of the present invention has extremely high wear resistance as described above. A resin composition having a wear resistance measured by the following method of 0 to 20%, particularly 5 to 15% can be obtained.
The measurement of wear resistance is carried out as follows. A test piece measuring 12.5 mm (width)xc3x97125 mm (length)xc3x973 mm (thickness) is formed by injection molding, annealed at room temperature for 48 hours, fixed to a jig with the entire surface measuring 125 mmxc3x973 mm as a wear testing surface, and rubbed with No. 600 sandpaper at a rate of 150 m/min and a contact bonding stress of 0.25 MPa to obtain the amount of wear, and the amount of wear is then divided by the weight of the test piece before the test to obtain wear resistance.
The wear resistant resin composition of the present invention is also excellent in terms of environmental preservation such as recyclability and the prevention of a harmful gas generated at the time of combustion, in addition to the above characteristic properties.
Therefore, the wear resistant resin composition of the present invention can be used as molded products and industrial parts such as interior and exterior parts of automovils, materials for covering rod-like and linear products, sheets, bottles, cases and pipes and also advantageously used in medical apparatuses, stationery, surface protective materials, construction sheets, cosmetic sheets, interior protective materials, water-barrier materials, decorative surface materials, food package materials, water-proofing materials and surface cover materials. Also the composition can be extremely advantageously used as a raw material for molded products which must have little influence upon environment and sanitation.